Polishing pad and method for manufacturing polished product

Abstract

To provide a polishing pad that maintains proper polishing performance and can be used for high-precision eddy current endpoint detection, and a method for manufacturing a polished product using the same.SOLUTION: A polishing pad comprises a polishing layer and a base layer laminated on the polishing layer, the base layer including magnetic particles.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a polishing pad and a polished workpiece. [Background technology]

[0002] In the semiconductor manufacturing process, chemical mechanical polishing (CMP) is used for planarization after insulating film deposition and for forming metal wiring. One of the important technologies required for chemical mechanical polishing is the polishing end point detection to detect whether the polishing process is complete. For example, over-polishing or under-polishing with respect to the target polishing end point directly leads to product defects. Therefore, in chemical mechanical polishing, it is necessary to strictly control the amount of polishing by detecting the polishing end point.

[0003] Chemical mechanical polishing is a complex process, and the polishing speed (polishing rate) changes depending on the operating conditions of the polishing equipment, the quality of consumables (slurry, polishing pads, dressers, etc.), and the influence of variations in conditions over time during the polishing process. Furthermore, in recent years, the accuracy of the remaining film thickness and the uniformity of the surface are becoming increasingly strict in the semiconductor manufacturing process. For these reasons, it is becoming more difficult to detect the polishing end point with sufficient accuracy.

[0004] Known main methods for detecting the polishing end point include an optical end point detection method, a torque end point detection method, and an eddy current end point detection method.

[0005] In the optical end point detection method, the wafer is irradiated with light through a transparent window member on the polishing pad, and the end point is detected by monitoring the reflected light. However, slurry may leak from around the window member during polishing, which may reduce the detection accuracy. In addition, it is necessary to provide a window member with different materials and physical properties on the polishing pad, which causes problems such as uneven polishing in the area where the window member is provided.

[0006] In the eddy current end point detection method, the end point is detected by using eddy currents that are generated in a conductive film on the wafer surface when magnetic lines pass through the conductive film. Examples of polishing pads used in such eddy current end point detection methods include a polishing pad with a recess on the back surface of the polishing layer to correspond to the driving and sensing coils (Patent Document 1), and a polishing pad with an end point detection area formed in the polishing body of a material different from the polishing body and recessed from the back surface of the polishing body (Patent Document 2). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Special Publication No. 2005-533667 [Patent Document 2] Special Publication No. 2013-539233 Summary of the Invention [Problem to be solved by the invention]

[0008] As described above, the polishing pads disclosed in Patent Documents 1 and 2 each have a recess or a recessed portion in a portion (hereinafter also referred to as the "end point detection area") corresponding to the film thickness detection sensor (coil). Therefore, the polishing pressure applied to the workpiece in the end point detection area differs from the polishing pressure applied to the workpiece on the polishing surface other than the end point detection area, resulting in a problem that the in-plane uniformity of polishing is impaired.

[0009] Furthermore, in the invention described in Patent Document 2, an end point detection region is provided which is a member separate from the polishing layer, and therefore slurry may leak from the periphery of the member, which may result in reduced detection accuracy.

[0010] The present invention has been made in consideration of the above problems, and aims to provide a polishing pad that can be used for highly accurate eddy current endpoint detection while maintaining appropriate polishing performance, and a method for manufacturing a polished workpiece using the same. [Means for solving the problem]

[0011] As a result of extensive investigations aimed at solving the above problems, the present inventors discovered that the above problems could be solved by using magnetic particles, leading to the completion of the present invention.

[0012] That is, the present invention is as follows. [1] A polishing layer and a base layer laminated on the polishing layer, The base layer contains magnetic particles. Polishing pad. [2] The abrasive layer does not contain magnetic particles. The polishing pad described in [1]. [3] The content of the magnetic particles is 0.01 to 30% by weight based on the total amount of the base layer. The polishing pad according to [1] or [2]. [4] The magnetic particles are soft magnetic particles. The polishing pad according to any one of [1] to [3]. [5] The magnetic particles are at least one selected from the group consisting of soft ferrite, permalloy, and silicon steel. The polishing pad according to [4]. [6] The method includes a polishing step of polishing a workpiece using the polishing pad according to any one of [1] to [5] to obtain a polished product, and an end point detection step of detecting an end point during the polishing. A method for manufacturing polished workpieces. Effect of the Invention

[0013] According to the present invention, it is possible to provide a polishing pad that can be used for highly accurate eddy current end point detection while maintaining appropriate polishing performance, and a method for manufacturing a polished product using the same. [Brief description of the drawings]

[0014] [Figure 1]1 is a schematic cross-sectional view of a polishing pad according to an embodiment of the present invention. [Diagram 2] FIG. 1 is a schematic diagram showing a film thickness control system installed in CMP. [Diagram 3] FIG. 2 is a schematic diagram showing the measurement principle of endpoint detection using an eddy current method. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Below, we will explain in detail the embodiment of the present invention (hereinafter referred to as the "present embodiment"). However, the present invention is not limited to this embodiment, and various modifications are possible without departing from the gist of the present invention.

[0016] [Polishing pad] The polishing pad of the present embodiment has a polishing layer and a base layer laminated on the polishing layer, and the base layer contains magnetic particles.

[0017] As shown in Fig. 1, the polishing pad 10 of this embodiment includes a polishing layer 11 and a base layer 12 having the same thickness in the end point detection region as in other regions. Therefore, compared to the case where a recess or a recessed portion is used, it is possible to maintain the desired polishing performance, such as ensuring the uniformity of the polishing surface and suppressing leakage of slurry, and it is possible to provide a polishing pad that can be used for highly accurate eddy current end point detection while maintaining appropriate polishing performance. The detailed configuration will be described below.

[0018] [Polishing layer] The polishing layer 11 has a polishing surface 11a for polishing an object to be polished. The configuration of the polishing layer is not particularly limited, and examples thereof include a foamed resin body, a non-foamed resin body, and a resin-impregnated substrate.

[0019] Here, the foamed resin body refers to a foamed resin body that does not have a fiber substrate. The foam shape is not particularly limited, but examples thereof include spherical bubbles, nearly spherical bubbles, teardrop-shaped bubbles, and open bubbles in which each bubble is partially connected.

[0020] In addition, the non-foamed resin molded body refers to a non-foamed body composed of a specific resin without a fiber substrate. The non-foamed body refers to a body that does not have bubbles as described above. In this embodiment, the non-foamed resin molded body also includes a body in which a curable composition is attached to a substrate such as a film and cured. More specifically, the non-foamed resin molded body also includes a resin cured product formed by a labia coater method, a small diameter gravure coater method, a reverse roll coater method, a transfer roll coater method, a kiss coater method, a die coater method, a screen printing method, a spray coating method, or the like.

[0021] Furthermore, the resin-impregnated substrate refers to a substrate obtained by impregnating a fiber substrate with a resin. The fiber substrate is not particularly limited, but examples thereof include woven fabric, nonwoven fabric, and knitted fabric.

[0022] (resin) The resin constituting the polishing layer may be a wet-solidifiable resin, a dry-solidifiable resin, or other curable resin, etc. These resins may be used alone or in combination of two or more kinds.

[0023] Here, "wet coagulation" refers to a method in which a resin solution in which a resin is dissolved is impregnated into a fiber substrate, and the fiber substrate is immersed in a bath of a coagulation liquid (such as water, which is a poor solvent for the resin), thereby coagulating and regenerating the resin in the impregnated resin solution. Alternatively, a resin solution in which a resin is dissolved may be applied to a film or the like, and the film may be immersed in a bath of the coagulation liquid to obtain a resin molded body that does not contain a fiber substrate. In this wet coagulation, the solvent in the resin solution is replaced with the coagulation liquid, so that the resin in the resin solution coagulates and coagulates. Note that bubbles are formed in areas other than the areas where the resin is coagulated and coagulated. The shape of the formed bubbles is not particularly limited, but they tend to be teardrop-shaped.

[0024] In addition, "dry solidification" refers to a method in which a liquid containing a prepolymer and a curing agent is impregnated into a fiber substrate, and the prepolymer and the curing agent are reacted to form a resin. Alternatively, a liquid containing a prepolymer and a curing agent may be applied to a film or the like, and the prepolymer and the curing agent are reacted to obtain a molded resin body that does not include a fiber substrate. In this wet solidification, a foam is obtained when gas is generated by the reaction between the prepolymer and the curing agent or when a foaming agent is used, and a non-foamed body is obtained in other cases. The foam shape is not particularly limited, but it tends to be mainly spherical or approximately spherical.

[0025] Specific examples of each resin are given below, but the resin constituting the polishing layer of this embodiment is not limited to the following.

[0026] Examples of resins that can be wet-solidified include, but are not limited to, polyurethane-based resins such as polyurethane and polyurethane polyurea; acrylic-based resins such as polyacrylate and polyacrylonitrile; vinyl-based resins such as polyvinyl chloride, polyvinyl acetate and polyvinylidene fluoride; polysulfone-based resins such as polysulfone and polyethersulfone; acylated cellulose-based resins such as acetylated cellulose and butyrylated cellulose; polyamide-based resins; and polystyrene-based resins.

[0027] Among these, it is preferable to include a polyurethane resin. Examples of the polyurethane resin include, but are not limited to, polyester polyurethane resin, polyether polyurethane resin, and polycarbonate polyurethane resin. By using such a resin, the polishing rate tends to be further improved.

[0028] The prepolymer constituting the dry-solidifiable resin is not particularly limited, but examples thereof include an adduct of hexamethylene diisocyanate and hexanetriol; an adduct of 2,4-tolylene diisocyanate and polyoxytetramethylene glycol; an adduct of tolylene diisocyanate and hexanetriol; an adduct of tolylene diisocyanate and trimethylolpropane; an adduct of xylylene diisocyanate and trimethylolpropane; an adduct of hexamethylene diisocyanate and trimethylolpropane; and an adduct of isocyanuric acid and hexamethylene diisocyanate. The prepolymer may be used alone or in combination of two or more kinds.

[0029] The curing agent constituting the dry-solidifying resin is not particularly limited, but examples thereof include amine compounds such as 3,3'-dichloro-4,4'-diaminodiphenylmethane, 4-methyl-2,6-bis(methylthio)-1,3-benzenediamine, 2-methyl-4,6-bis(methylthio)-1,3-benzenediamine, 2,2-bis(3-amino-4-hydroxyphenyl)propane, 2,2-bis[3-(isopropylamino)-4-hydroxyphenyl]propane, 2,2-bis[3-(1-methylpropylamino)-4-hydroxyphenyl]propane, 2,2-bis[3-(1-methylpentylamino)-4-hydroxyphenyl]propane, 2,2-bis(3,5-diamino-4-hydroxyphenyl)propane, 2,6-diamino-4-methylphenol, trimethylethylenebis-4-aminobenzoate, and polytetramethylene oxide-di-p-aminobenzoate; ethylene glycol, propylene glycol, and the like. Examples of polyhydric alcohol compounds include polyhydric alcohol compounds such as ethylene glycol, diethylene glycol, trimethylene glycol, tetraethylene glycol, triethylene glycol, dipropylene glycol, 1,4-butanediol, 1,3-butanediol, 2,3-butanediol, 1,2-butanediol, 3-methyl-1,2-butanediol, 1,2-pentanediol, 1,4-pentanediol, 2,4-pentanediol, 2,3-dimethyltrimethylene glycol, tetramethylene glycol, 3-methyl-4,3-pentanediol, 3-methyl-4,5-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, 1,6-hexanediol, 1,5-hexanediol, 1,4-hexanediol, 2,5-hexanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, glycerin, trimethylolpropane, trimethylolethane, and trimethylolmethane. The curing agents may be used alone or in combination of two or more.

[0030] Other compositions constituting the curable resin are not particularly limited, and may be, for example, a photocurable composition containing a photopolymerization initiator and a polymerizable compound, a thermosetting composition containing a thermal polymerization initiator and a polymerizable compound, a thermosetting resin, a UV-curable resin, or a two-liquid mixed curable resin. The curable composition may also contain a crosslinking agent having two or more polymerizable functional groups, as necessary.

[0031] The polymerizable compound is not particularly limited, but examples thereof include (meth)acrylate, epoxy (meth)acrylate, urethane (meth)acrylate, and polyester (meth)acrylate.

[0032] The photopolymerization initiator is not particularly limited, but examples thereof include benzophenone-based compounds, acetophenone-based compounds, and thioxanthones. The thermal polymerization initiator is not particularly limited, but examples thereof include azo compounds such as 2,2'-azobisbutyronitrile, and peroxides such as benzoyl peroxide (BPO).

[0033] The thermosetting resin is not particularly limited, but examples thereof include phenol resin, epoxy resin, acrylic resin, urea resin, and formaldehyde resin.

[0034] The UV-curable resin is not particularly limited, but examples thereof include prepolymers having a number average molecular weight of about 1,000 to 10,000, acrylic (methacrylic) esters and their urethane modifications, thiokol-based compounds, etc., and reactive diluents and organic solvents can be used as appropriate depending on the application.

[0035] The two-liquid mixed curable resin is not particularly limited, but for example, prepolymers having different physical properties can be used.

[0036] Since the abrasive layer comes into direct contact with the workpiece to be polished, it is preferable not to include magnetic particles, particularly in the case of polishing semiconductors, since magnetic particles may adversely affect the semiconductor.

[0037] [Base material layer] The polishing pad of this embodiment has a base layer on the opposite side of the polishing surface of the polishing layer. By having the base layer, the conformability to the workpiece to be polished is improved, and the uniformity of the polishing pressure on the workpiece tends to be improved.

[0038] The substrate layer is not particularly limited, and examples thereof include impregnated nonwoven fabrics and resin foams impregnated with resin. Examples of impregnated nonwoven fabrics include polyolefin-based, polyamide-based, polyester-based, and other nonwoven fabrics impregnated with polyurethane-based resins such as polyurethane and polyurethane polyurea, acrylic-based resins such as polyacrylate and polyacrylonitrile, vinyl-based resins such as polyvinyl chloride, polyvinyl acetate, and polyvinylidene fluoride, polysulfone-based resins such as polysulfone and polyethersulfone, acylated cellulose-based resins such as acetylated cellulose and butyrylated cellulose, polyamide-based resins, and polystyrene-based resins. Examples of resin foams include polyolefin-based foams, polyurethane-based foams, polystyrene-based foams, phenol-based foams, synthetic rubber-based foams, and silicone rubber-based foams.

[0039] (Magnetic particles) The base layer contains magnetic particles. The magnetic particles are not particularly limited, but may be, for example, soft magnetic material with small coercive force and large magnetic permeability, hard magnetic material with large coercive force, and magnetic resistance material whose electric resistance changes when a magnetic field is applied. Among these, soft magnetic materials such as soft ferrite, permalloy, and silicon steel are preferred. By using such magnetic particles, the accuracy of eddy current end point detection tends to be improved. Unlike the polishing layer, the base layer does not directly contact the object to be polished, so even if magnetic particles are included, there is little possibility that they will adversely affect polishing.

[0040] The content of the magnetic particles is preferably 0.01 to 30% by weight, more preferably 0.05 to 20% by weight, and even more preferably 0.1 to 10% by weight, based on the total weight of the base layer. By having the content of the magnetic particles within the above range, the accuracy of the eddy current end point detection tends to be further improved. In addition, the average particle size of the magnetic particles is preferably 3.5 to 200 μm, more preferably 5 to 150 μm, and even more preferably 10 to 100 μm.

[0041] [Method of manufacturing polishing pad] The polishing pad of this embodiment can be manufactured by known methods such as a method of bonding a polishing layer and a base layer together, or a method of forming a polishing layer on a base layer.

[0042] The method for forming the polishing layer is not particularly limited, but examples thereof include the above-mentioned wet solidification method, the above-mentioned dry solidification method, and a method of curing a curable resin.

[0043] The method for forming the base layer is not particularly limited, and may be, for example, a method for forming each of the above foams by a known method. In this embodiment, when magnetic particles are contained in the base layer, the magnetic particles can be mixed into the matrix resin of the foam at the stage of forming the foam.

[0044] [Method for manufacturing polished product] The method for producing a polished product of this embodiment includes a polishing step of polishing a workpiece using the polishing pad to obtain a polished product, and an end point detection step of detecting an end point during the polishing.

[0045] [Polishing process] The polishing process may be a primary lapping process (rough lapping), a secondary lapping process (finish lapping), a primary polishing process (rough polishing), a secondary polishing process (finish polishing), or a process that combines these processes. Note that, here, "lapping" refers to polishing at a relatively high rate using coarse abrasive grains, and "polishing" refers to polishing at a relatively low rate using fine abrasive grains to improve the surface quality.

[0046] Among these, the polishing pad of the present embodiment is preferably used for chemical mechanical polishing. Hereinafter, the method for producing the polished product of the present embodiment will be described taking chemical mechanical polishing as an example, but the method for producing the polished product of the present embodiment is not limited to the following.

[0047] The object to be polished is not particularly limited, but examples thereof include materials such as semiconductor devices and electronic components, particularly thin substrates (objects to be polished) such as Si substrates (silicon wafers), SiC (silicon carbide) substrates, GaAs (gallium arsenide) substrates, glass, substrates for hard disks and LCDs (liquid crystal displays), etc. In particular, semiconductor devices having metal wiring such as W (tungsten) and Cu (copper) are included.

[0048] The polishing method may be a conventionally known method, and is not particularly limited. For example, first, the object to be polished held on a holding platen arranged to face the polishing pad is pressed against the polishing surface, and the polishing pad and / or the holding platen are rotated while supplying a slurry from the outside. The polishing pad and the holding platen may rotate in the same direction at different rotation speeds, or in different directions. The object to be polished may be polished while moving (rotating) inside the frame during the polishing process.

[0049] The slurry may contain water, chemical components such as an oxidizing agent such as hydrogen peroxide, additives, abrasive grains (polishing particles; for example, SiC, SiO2, Al2O3, CeO2), etc. depending on the object to be polished and the polishing conditions.

[0050] [End point detection process] The manufacturing method of the polished workpiece of this embodiment has an end point detection step of detecting the end point by an eddy current method in the above-mentioned polishing step. As the end point detection method by the eddy current method, specifically, a conventionally known method can be used. FIG. 2 shows a schematic diagram of the end point detection method by the eddy current method. This schematic diagram shows a chemical mechanical polishing process in which a wafer W held by a top ring 21 is pressed against a polishing pad 10 attached on a table 22 while a slurry (not shown) is flowed, thereby polishing and flattening the uneven film on the surface of the wafer W. The polishing device 20 is equipped with a film thickness detection sensor 23 on the table 22 to monitor the film thickness in order to end the process with a predetermined film thickness at the same time as the flattening. The films to be monitored include metal films and insulating films, and the film thickness detection sensor 23 by the eddy current method is equipped for detecting the metal film.

[0051] 3, magnetic field lines H1 are generated in a direction penetrating the table 22 from the film thickness detection sensor 23 provided at a position passing through the center of the wafer W on the table 22, and if a conductive film W1 is present on the wafer W, eddy currents C are generated on the surface of the wafer W when the magnetic field lines pass through the conductive film W1. When the eddy currents flow, magnetic field lines H2 are generated in the opposite direction to the magnetic field lines from the film thickness detection sensor 23. Since the resistance of the eddy currents changes depending on the thickness of the metal film W1, by measuring the strength of the magnetic field lines H2 in the opposite direction, the thickness of the metal film W1 during polishing can be identified and the end point can be detected.

[0052] Films that can be measured using the eddy current method are metal films such as Cu and W. Figure 3 shows an image of eddy current generation. As polishing of the wafer W progresses, the metal film W1 on the surface of the wafer W decreases. The output of the eddy current sensor 23 changes accordingly, measuring the amount of film thickness change, and it can be confirmed that the end point at which the metal film W1 is completely removed is detected. EXAMPLES

[0053] The present invention will be described in more detail below using examples and comparative examples, but the present invention is not limited to the following examples.

[0054] (Preparation of abrasive layer A) A prepolymer containing an adduct of 2,4-tolylene diisocyanate and polyoxytetramethylene glycol was added with 3,3'-dichloro-4,4'-diaminodiphenylmethane as a curing agent, and cured to form the polishing layer A.

[0055] (Preparation of substrate layer a) A nonwoven fabric made of polyethylene fibers was impregnated with a polyurethane resin solution, then wet-coagulated and dried to obtain a base layer a that did not contain magnetic particles.

[0056] (Preparation of substrate layer b) Substrate layer b was obtained in the same manner as substrate layer a, except that Ni-Zn-Cu ferrite powder with an average particle size of 30 μm was added as magnetic particles to the polyurethane resin solution of substrate layer a so as to account for 5 weight % of the total amount of the substrate layer.

[0057] (Preparation of base layer c) Substrate layer c was obtained in the same manner as substrate layer a, except that Ni-Zn-Cu ferrite powder with an average particle size of 30 μm was added as magnetic particles to the polyurethane resin solution of substrate layer a so as to account for 10 weight % of the total amount of the substrate layer.

[0058] (Measurement of magnetic permeability) A magnetic permeability measuring tool (e.g., Agilent's 16454A) was connected to a network analyzer (e.g., Agilent's E5071C), and a doughnut-shaped sample punched to an outer diameter of 7 mm and an inner diameter of 3 mm was set on the tool, and the magnetic permeability was measured using a predetermined program. The magnetic permeabilities of the polishing layer A and the base layers a to c were as shown in Tables 1 and 2 below.

[0059] [Table 1]

[0060] [Table 2]

[0061] Examples and Comparative Examples As shown in Table 3 below, polishing layers and base layers were combined to prepare polishing pads of the examples and comparative examples. The polishing pad of Comparative Example 2 was a conventionally known polishing pad IC1000 (manufactured by Nitta Haas Corporation). The magnetic permeability μ all was measured. [Table 3]

[0062] In both Examples 1 and 2, the magnetic permeability μ all was increased by more than one order of magnitude, and eddy current end point detection was possible with high accuracy. [Industrial Applicability]

[0063] The polishing pad of the present invention has industrial applicability as a pad that is suitably used for polishing a device in which a conductive layer or the like is formed on a semiconductor wafer. [Explanation of symbols]

[0064] 10: polishing pad, 11: polishing layer, 11a: polishing surface, 12: base layer, 20: polishing device, 21: top ring, 22: table, 23: film thickness detection sensor, W: wafer, W1: metal film, H1, H2: magnetic field lines, C: eddy current

Claims

1. A polishing layer and a base layer laminated on the polishing layer, The base layer contains magnetic particles. Polishing pad.

2. The abrasive layer does not contain magnetic particles. The polishing pad of claim 1.

3. The content of the magnetic particles is 0.01 to 30% by weight based on the total amount of the base layer.

3. The polishing pad according to claim 1 or 2.

4. The magnetic particles are soft magnetic particles. The polishing pad according to any one of claims 1 to 3.

5. The magnetic particles are at least one selected from the group consisting of soft ferrite, permalloy, and silicon steel. The polishing pad of claim 4.

6. The method includes a polishing step of polishing a workpiece by using the polishing pad according to any one of claims 1 to 5 to obtain a polished product, and an end point detection step of detecting an end point during the polishing. A method for manufacturing polished workpieces.

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